Question

存储过程中如何执行带输出参数的动态SQL

Answer 1

SQL Server存储过程中执行带输出参数的动态sql是很多人经常碰到的问题，比如根据一些条件查询列表，并返回记录数等。下面是一个参考示例，查询用户列表，它可以利用临时表实现翻页，并带有死锁和超时检测功能。 CREATE PRocedure pUserList ( @UserType char(2), @pagenum int, @perpagesize int, @pagetotal int out, @rowcount int out ) as set nocount on DECLARE @Err INT,@ErrCounter INT declare @sql nvarchar(2000) --声明动态sql执行语句 declare @pagecount int --当前页数 declare @sWhere nvarchar(200) declare @sOrder nvarchar(100) set @sWhere = ' where 1=1 ' if not(@UserType is null) set @sWhere = @sWhere + ' and UserType = ' + @UserType set @sOrder = ' order by UserID ' --取得当前数据库的记录总数 declare @row_num int LockTimeOutRetry: --创建临时表，作为数据过滤 create table #change (T_id int) set @sql = 'select @row_num=count(*) from dbo.[User]' + @sWhere exec sp_executesql @sql,N'@row_num int output', @row_num output if @row_num % @perpagesize =0 set @pagetotal = @row_num/@perpagesize else set @pagetotal = @row_num/@perpagesize + 1 set @rowcount = @row_num if @row_num > @perpagesize begin set @row_num = @pagenum * @perpagesize if @row_num = @perpagesize begin set @sql = N'select top ' + cast(@perpagesize as varchar) + ' UserID,LoginName,RealName from dbo.[User]' + @sWhere + @sOrder exec sp_executesql @sql SET @Err = @@ERROR IF @Err <> 0 GOTO ErrorHandler return 0 end else begin set @row_num = (@pagenum-1) * @perpagesize set @pagecount = @row_num set @sql=N'insert #change (T_id) select top ' + cast(@pagecount as varchar) + ' UserID from dbo. [User] '+@sWhere+' and UserID not in (select T_id from #change)' + @sOrder exec sp_executesql @sql set @sql = N'select top ' + cast(@perpagesize as varchar) + ' UserID,LoginName,RealName from dbo.[User] '+@sWhere+' and UserID not in (select T_id from #change)' + @sOrder exec sp_executesql @sql SET @Err = @@ERROR IF @Err <> 0 GOTO ErrorHandler return 0 end end else begin set @sql = 'select UserID,LoginName,RealName from dbo.[User]' + @sWhere + @sOrder exec sp_executesql @sql SET @Err = @@ERROR IF @Err <> 0 GOTO ErrorHandler return 0 end ErrorHandler: IF (@Err = 1222 OR @Err = 1205) AND @ErrCounter = 5 BEGIN RAISERROR ('Unable to Lock Data after five attempts.', 16,1) return -100 END IF @Err = 1222 OR @Err = 1205 -- Lock Timeout / Deadlock BEGIN WAITFOR DELAY '00:00:00.25' SET @ErrCounter = @ErrCounter + 1 GOTO LockTimeOutRetry END -- else unknown error RAISERROR (@err, 16,1) WITH LOG return -100 GO SET QUOTED_IDENTIFIER OFF GO SET ANSI_NULLS ON GO SET QUOTED_IDENTIFIER ON GO SET ANSI_NULLS ON GO

Answer 2

MSSQL为我们提供了两种动态执行SQL语句的命令，分别是EXEC和sp_executesql;通常,sp_executesql则更具有优势，它提供了输入输出接口，而EXEC没有。
exec演示：
DECLARE @TableName VARCHAR(50),@Sql NVARCHAR (MAX),@OrderID INT;
--申明变量
SET @TableName = 'Orders'; --设置值也就是赋值
SET @OrderID = 10251;
SET @sql ='SELECT * FROM '+QUOTENAME(@TableName) +'WHERE OrderID = '+CAST(@OrderID AS VARCHAR(10))+' ORDER BY ORDERID DESC'
EXEC(@sql); -- 执行带参数的sql语句
sp_executesql命令在SQL Server中引入的比EXEC命令晚一些，它主要为重用执行计划提供更好的支持。
DECLARE @TableName VARCHAR(50),@sql NVARCHAR(MAX),@OrderID INT ,@sql2 NVARCHAR(MAX); --申明变量
SET @TableName = 'Orders '; ---设置值也就是赋值
SET @OrderID = 10251;
SET @sql = 'SELECT * FROM '+QUOTENAME(@TableName) + ' WHERE OrderID = '+CAST(@OrderID AS VARCHAR(50)) + ' ORDER BY ORDERID DESC'
EXEC sp_executesql @sql -- 执行带参数的sql语句